Configuration of implanted devices

ABSTRACT

An arrangement for implanted medical devices in which the implant ( 20 ) includes certain parameters ( 21 ) stored in memory. Upon initialisation, these parameters are downloaded to the external component ( 30 ). This allows for simpler changes to the external device, or for a generic external device to be used. A particular application is to Cochlear implants.

FIELD OF THE INVENTION

[0001] The present invention relates to implanted medical devices, forexample cochlear implants, which combine an implanted device with anexternal, continuously linked device to provide the requiredfunctionality.

BACKGROUND ART

[0002] Medical devices of various types operate using an implantedcomponent, and an external unit which is required to be linked to theimplanted component, for example by an RF or inductive link, to providethe required functionality. The following discussion will be principallyin the context of cochlear implants, but other similar issues arise fordevices such as spinal, visual or other neural stimulators, and othermedical implant applications.

[0003] In the case of cochlear implants, the system is generallyconfigured as an external speech processor, and an implantedreceiver/stimulator device. The internal device includes an electrodearray-for providing electrical stimuli to the cochlea, electricalcircuitry to generate the stimuli, and a means for receiving signals andpower from the external speech processor. One arrangement, generallyused in devices manufactured by the applicant, uses an inductive link totransfer power and data between the external speech processor unit andthe implanted receiver/stimulator device. For the purposes of thisinvention however, the precise mechanism used is not presently relevant.

[0004] Conventionally cochlear implant devices have been arranged suchthat the implanted unit responds to commands from a compatibleprocessor, but does not store patient specific data or identificationcodes in such a way so as to exclude the implanted unit responding toany processor unit. In conventional systems the patient specific dataand programming is stored in the external speech processor and there isno data retained in the implant when it is powered down.

[0005] One issue with such devices is that in some situations, forexample in a facility for the hearing impaired, it is possible for usersto inadvertently swap speech processors. Each speech processor willcontain a set of data specific to each individual—for example, speechprocessing strategies, stimulus coding strategies and electrode mappingparameters. If the wrong speech processor is used for a patient, thenthe use of the incorrect parameters will cause at best poor speechperception by the user, and at worst may cause pain and discomfort.Present cochlear implant systems do not incorporate mechanisms toprevent such a problem arising.

[0006] Similarly, if the speech processor is lost or damaged, the onlyrecord of the appropriate parameters for the patient is stored at theclinic which provided the programming for the processor. The clinicianneeds to then access the patients records and identify the implantserial number to initiate a programming session. If this is not readilyavailable, then a new speech processor must be programmed from thebeginning, which is a complex and time consuming process. Similar issuesarise for other implanted devices which use an external component toprovide ongoing data to an implant.

[0007] With this in mind, one object of the present invention is toprovide an implanted device which allows for desired operation of thedevice through use of a compatible generic external component.

[0008] A further object of the present invention is a system whichprevents inadvertent operation of an implanted medical device withincorrect parameters.

[0009] Yet a further object of the present invention is a system whichallows for a simple process of exchanging external processors andaccessing of patient specific data.

SUMMARY OF THE INVENTION

[0010] Broadly, the present invention provides a change in the paradigmof where the patient specific data is stored. Instead of the implanteddevice being essentially undifferentiated and the external processorcustomised, the implanted device is used to store the user specificparameters, which are downloaded by the external processor each time itis first brought into operational mode. As a consequence, the externalprocessor need not be customised, and in a preferred implementation isessentially a generic device, which is customised by the parametersdownloaded from the implant each time it is turned on. Additionally,during operation the external processor is preferably continuallychecking that it is still connected to the same implant, for example byperiodic interrogation of the implant and receiving an expected serialnumber.

[0011] This approach allows for the external processor to be customisedto the active implant, regardless of which user currently is inpossession, subject of course to compatibility of the external processorand the implant. This also allows, for example, simplified use of areplacement external processor. The necessary parameters are carried ina suitable memory device in the implant, and uploaded at the start ofoperation to the external processor. This may be readily achieved byusing the telemetry link which already exists in many available devices.The processor may also detect the type or model of the implant, and soselect the appropriate operational mode.

BRIEF DESCRIPTION OF DRAWINGS

[0012]FIG. 1 is an illustration of a typical cochlear implant system;

[0013]FIG. 2A illustrates the division of function within a prior artcochlear implant; and FIG. 2B illustrates the division of functionwithin a cochlear implant device according to the present invention.

DETAILED DESCRIPTION

[0014] The present invention will be explained principally in thecontext of cochlear implants. However, it will be appreciated by thoseskilled in the art that the same principle is readily implemented inother applications.

[0015]FIG. 1 illustrates a typical cochlear implant system having anexternal component, including a speech processor 1, and an internalcomponent including an implanted receiver and stimulator unit 6. Theexternal component includes a microphone 2. The speech processor is inthis illustration constructed and arranged so that it can fit behind theouter ear 11. Alternative versions may be worn on the body. Attached tospeech processor 1 is a transmitter coil 3 which transmits theelectrical signals to the implanted unit 6 via an RF link 4.

[0016] The implanted component includes a receiver coil 5 for receivingpower and data from transmitter coil 3. A cable 7 extends from theimplanted device 6 to the cochlea 12 and terminates in an electrodearray 10. The signals thus received are applied by the array 10 to thebasilar membrane 8 thereby stimulating the auditory nerve 9. Theoperation of the device shown in FIG. 1 is described, for example, inU.S. Pat. No. 4,532,930.

[0017] Thus, the RF link, which is in turn powered by the speechprocessor 1, provides power and data to the implanted device 6. Thespeech processor also processes sound signals received by microphone 2,so as to send appropriate processed audio information or stimulus and/orcontrol commands to the implanted device 6. The precise details ofspeech processing are not necessary for an understanding of the presentinvention, and the skilled worker in the art will be aware that manysuch schemes have been used and proposed. Virtually all such schemesrely on patient specific data. For example, post implantation it isusual for the implanted electrodes in a multi-electrode array to betested for function, and for the sound percepts which are generated bystimuli to particular electrode pairs to be determined. These electrodespecific percepts used in conjunction with a stimulation strategy togenerate a patient specific map. Different patients have differentspeech processing strategies, and different parameters within a givenspeech processing strategy. Further, each user may have a uniquestimulus coding strategy. Other data may also be stored, for examplealternative speech processing schemes and the user specific strategy forthose schemes, or data of other types. All these data will be discussedas user specific parameters for the purposes of the discussion below,and are well understood by those skilled in the art.

[0018] Commercially available cochlear implant systems have in somecases a telemetry system in place. This allows for various parameterssensed by the implant to be sent back via the communications link to thespeech processor. Conventional telemetry data may include data on theoperation of the implant, as well as sensor data to assist in definingstimulus and speech processing strategies and for diagnostics.

[0019]FIG. 2A illustrates the conceptual operation of a conventionaldevice. The user parameters 31 are stored in non-volatile memory in theexternal processor 30. The external processor 30 communicates viacommunications link 25 with the implant 20. Instructions as to theelectrical stimuli to be delivered are sent to the implant, andtelemetry data is sent back from the implant, via communications link25.

[0020]FIG. 2B illustrates the conceptual approach of the presentinvention. Implant 20 includes user parameters 21, and a serial number22, stored in non-volatile memory. The parameters would be initially setusing a programming mode using data derived from clinical andaudiological tests, as is conventional. However, instead of this databeing stored in the external processor 30, it is stored in the implant.It will be appreciated that the user parameters 21 could be in a codedformat to minimise the data required to be downloaded during start-up.The serial number 22 could be implemented in various ways, including theuse of a fixed serial number. An alternative would be a value set as aresult of a handshake at start up with the external processor, so thatthe value is changed with each new start-up. Such mechanisms are wellknown in the communications field, and the exact form of interaction isnot crucial. It is important however, that there is some form ofon-going check, so that the external processor continues to send signalsonly when the correct implant is interoperating.

[0021] The processor 30 according to the present invention includes avolatile memory 32 for storing the user parameters downloaded during thestart-up process. This may be strictly a volatile memory, or merely onewhich is reused. It is highly preferred that this data is not retainedby the speech processor, and the processor operates only on data that isdownloaded each time it is powered up and recognizes the implant. Theexternal processor 30 also includes code 33 necessary to perform theon-going check of serial number, as discussed above.

[0022] As can be seen from FIG. 2, the communications link carries notonly telemetry, but also serial number data and, at start up, the userparameters from the implant to the external processor. The link 25carries processed audio information or stimulus and/or control commands,as well as signals relating to the on-going check of the connection.

[0023] As it is not simply a master/slave relationship, the externalprocessor and implant need to complete a start up procedure each timethe speech processor is turned on. A suitable procedure is as follows:

[0024] 1. The speech processor is not receiving back telemetry signals,and so it sends an implant interrogation sequence.

[0025] 2. The implant responds to the interrogation sequence.

[0026] 3. The speech processor identifies the implant, for example modeland number, and requests download of user parameters.

[0027] 4. The speech processor configures itself according to the userparameters and implant data downloaded.

[0028] 5. The speech processor starts signal processing and mapping,stimulus and/or command encoding based upon the downloaded data. A“handshake” with the implant is maintained continuously.

[0029] Step 5 may involve a simple low-rate handshake, for example anacknowledgement sequence sent for example, 100 ms or for the system at arate low enough to identify when the communication link is broken, butnot so low that the system does not recognise that a new device has beenswapped. Alternatively, a higher rate handshake, such as a compliancetelemetry response in each stimulus frame, could be used.

[0030] It will be appreciated the present invention can be readilyapplied to any implanted device required to operate with an externaldevice to provide normal function. It will be apparent to those skilledin the art that variations and additions are possible within the generalinventive concept.

1. An implantable medical device system, of the type including animplant, an external processor, and a communications link operativelyprovided between the implant and the external processor, said systembeing of the type in which parameters specific to a given user orimplant are required to be applied in said external processor, and theexternal processor operatively provides on-going information derivedfrom said parameters to said implant, characterized in that said implantincludes memory means storing at least some of said parameters, and saidimplant is adapted to download said parameters to said processor.
 2. Animplantable medical device system according to claim 1, wherein saidparameters include parameters specific to the user, and parametersspecific to said implant.
 3. An implantable medical device systemaccording to claim 2, wherein operatively said communications link isactive bi-directionally, so that said implant provides data to saidexternal processor indicating its identity.
 4. An implantable medicaldevice system according to claim 1, wherein said implant is a neuralstimulation device.
 5. An implantable medical device system according toclaim 4, wherein said implant is an auditory neural stimulation device.6. A medical implant, adapted to operatively communicate using acommunications link with an external processor, said external processoroperatively providing on-going instructions to said implant, and saidprocessor requiring parameters specific to a given user to generate saidinstructions, said implant being characterized in that it includesmemory means storing at least some of said parameters, and said implantis adapted to download said parameters to said processor.
 7. An implantaccording to claim 6, wherein said parameters include parametersspecific to the user, and parameters specific to said implant.
 8. Animplant according to claim 7, wherein operatively said communicationslink is active bi-directionally, so that said implant is adapted toprovide data to said external processor indicating its identity.
 9. Animplant according to claim 6, wherein said implant is a neuralstimulation device.
 10. An implant according to claim 9, wherein saidimplant is an auditory neural stimulation device.
 11. An externalprocessor for use with an implanted medical device, of the type in whicha communications link is operatively provided between the implantedmedical device and the external processor, said system being of the typein which parameters specific to a given user are required to be appliedin said processor, and the external processor operatively provideson-going information derived from said parameters to said implantedmedical device, characterized in that said external processor is adaptedto receive parameters downloaded from said implant for use in saidexternal processor, said parameters being downloaded when said processoris placed in an operative state.
 12. An external processor according toclaim 11, wherein said parameters are not retained in said processor forre-use when said processor is next placed in an operative state.
 13. Anexternal processor according to claim 12, said parameters includeparameters specific to the user, and parameters specific to saidimplant.
 14. An external processor according to claim 13, whereinoperatively said communications link is active bi-directionally, saidprocessor being adapted to receive data from said implant indicating theidentity of the implant, and if said information is not received in apredefined manner, said external processor shuts down.
 15. An externalprocessor according to claim 11, wherein the external processor isadapted for use with an implant being a neural stimulation device. 16.An external processor according to claim 15, wherein the externalprocessor is adapted for use with an implant being an auditory neuralstimulation device.
 17. A method for providing implant or user specificparameters in an implantable medical device system, said systemincluding an exernal processor, on implant, and a communications linkbetween said implant and said external processor, said method includingat least the steps of: said processor transmitting an initialisationsignal; said implant receiving said initialisation signal; andtransmitting from memory a set of parameters; said processor receivingsaid set, and processing said set so that said parameters are availablefor operative use.
 18. A method according to claim 17, wherein saidmethod further includes periodic signals being transmitted from saidimplant to said processor, and if a predetermined number of said signalsare not received, said processor switches to an inoperative mode.
 19. Amethod according to claim 17, wherein the set of parameters includes oneor more of user specific parameters, and implant specific parameter.